The present invention relates to a reamer section drill and more particularly to an improved vertical feed type burnishing drill.
Various types of drilling tools are known which are adapted to ream a hole of a desired diameter while cutting the wall of the hole. Such drilling tools are a single-purposed, exclusive and/or automated tool which can be increased in cutting efficiency and used to provide high-quality and uniform products.
Japanese Utility Model Laid-Open Application No. 62-65107 discloses a reamer section drill including two drilling edges and four reaming edges, all these edges being arranged in the same circle.
FIGS. 4 and 5 in the accompanying drawings show another burnishing drill. Such a burnishing drill comprises a cylindrical drill body 2 connected with a shank 1, the drill body 2 includes cutting edges 5, formed therein, at the tip 3 thereof, and opposed to each other diametrically about the longitudinal axis of the drill body 2. Each of the cutting edges 5 includes a slant face 6 extending therefrom rearwardly in the direction of rotation (shown by arrow A in FIG. 5) and a guide face 7 axially extending from the edge of the slant face 6. The drill body 2 further includes a longitudinally extending relief surface 8 formed therein between each of the cutting edges 5 and the corresponding guide face 7 at the outer wall of the drill body 2 and a longitudinally extending relief groove 9 formed in the drill body 2.
This drill does not have good centering and stabilizing properties since the initial bite cannot be properly made. As a result, the drilled hole made is excessively reamed and its inner wall is rough.